Types of Spinal Fractures
Classifying the various types of spinal fractures can be confusing because there are several classification methods. We'll focus on the most basic and the most generally accepted classifications for spinal fractures.
Denis Classification: The Three-column Concept
This system divides the spine into three columns (when viewing the spine from the side):
- Anterior Column: This is the front part of the vertebra—the part that faces in towards your body. The anterior column is the front half of the vertebral body and intervertebral disc. There's a ligament on the front of the spine called the anterior longitudinal ligament; that's part of the anterior column as well.
- Middle Column: This is the key part of spinal stability. It's the back half of the vertebral body and intervertebral disc. There's a ligament on the back of the vertebral body called the posterior longitudinal ligament; that's part of the middle column as well. If there's a fracture in the middle column in addition to the anterior or posterior column, you're much more likely to have nerve damage and spinal instability. As long as the middle column stays intact, you have a better chance of having a stable fracture.
- Posterior Column: All the parts of the vertebra that are on the back side make up the posterior column. This includes the pedicles, lamina, facet joints, and spinous process (that's the bony part you can feel when you run your finger up your spine).
The three-column concept makes it easier to visualize spinal fractures. It also makes it easier to understand why some fractures are more stable than others. For example, if you have a fracture just in the anterior column, the spine should be able to still carry your weight well enough.
However, if you fracture the anterior and middle column, it's more likely that your spine will be unstable. Since the middle column connects the anterior and posterior columns, if that part is fractured, it will be harder for the spine to function well.
Major and Minor Fractures
This is the simplest way to talk about fractures: major or minor.
A minor fracture means that a part of the posterior (back side) elements of the vertebra has broken—the parts that aren't as vital to spinal stability. The posterior elements include the spinous process and the facet joints (also called the articular processes). If you fracture this part of the vertebrae, it's usually not too serious.
A major fracture means that part of the vertebral body, the pedicles, or the lamina has fractured. Fracturing the vertebral body is considered major because it helps carry so much weight and distribute the force of your movements. If it's broken, you can have serious problems with the vertebrae lining up correctly. Fracturing the pedicles or lamina is dangerous because of the increased possibility of nerve damage. Additionally, the pedicles and lamina provide a lot of necessary support to keep your spine stable. If they fracture, your spine may be unstable.
Stable and Unstable Fractures
Stable and unstable is another basic classification for spinal fractures.
Stable fractures don't cause spinal deformity or neurologic (nerve) problems. With a stable fracture, the spine can still carry and distribute your weight pretty well (not as well as if there weren't a fracture, but it's still able to function with a stable fracture).
Unstable fractures make it difficult for the spine to carry and distribute weight. Unstable fractures have a chance of progressing and causing further damage. They may also cause spinal deformity.
Specific Fracture Types
Beyond whether a fracture is stable or unstable, major or minor, you should understand the different ways a vertebra can break. As your doctor describes your fracture, you may hear terms such as:
- Compression Fracture: This type of fracture is very common in patients with osteoporosis, or patients whose bones have been weakened by other diseases (such as bone cancer). The vertebra can absorb so much pressure; if there's a sudden force of a lot of pressure, the bone may not be able to handle the stress. The vertebra can fracture then.
A wedge fracture is a subtype of compression fracture. With a wedge fracture, part of the vertebra—usually the anterior (front) part—collapses under pressure and becomes wedge shaped.
- Burst Fracture: Burst fractures are caused by severe trauma (e.g., car accident). They happen when the vertebra is essentially crushed by extreme forces. Unlike compression fractures, it's not just one part of the vertebra that's fractured. In a burst fracture, the vertebra is fractured in multiple places. Because the vertebra is crushed completely, bony fragments can spread out and cause spinal cord injury. Burst fractures are more severe than compression fractures.
- Flexion-distraction Fractures: If you're in a car accident where your body is pushed forward, you may get a flexion-distraction fracture. Your spine is made to flex forward, but if there's a sudden forward movement that places incredible stress on the spine, it may break a vertebra or vertebrae. Thinking of the three-column concept, a flexion-distraction fracture usually has fractures in the posterior and middle column.
- Fracture-dislocation: If you have any of the above fractures and the vertebra(e) moves significantly (dislocation), you have a fracture-dislocation. Usually, these fractures involve all three columns from the three-column concept, and they make your spine very unstable.